Dataset: Estimating seagrass carbon stocks to inform NetZero targets: Spatiotemporal insights from a protected tidal lagoon

Conserving and managing seagrass ecosystems for their sedimentary organic carbon (SOC) stock in climate change mitigation and other ecosystem services is an increasingly important strategy in the face of increasing anthropogenic threats. In South Africa, there is limited data on how seagrass SOC stocks vary spatially and temporally. Langebaan Lagoon, South Africa’s only estuarine lagoon and a marine protected area (MPA), provides a unique natural laboratory for addressing knowledge gaps, while contributing to regional and global seagrass SOC data. To measure SOC to a depth of 50 cm, we collected 70 sediment cores across continuous and patchy (as well as some cores from unvegetated sediments) mono-specific meadows of the seagrass <i>Zostera capensis</i> across five sites, spanning the extent of the lagoon system and its seagrass cover. Cores were collected using a stainless steel Russian peat corer (5 cm diameter x 50 cm length). Cores were sub-sectioned into five depth intervals (0–5, 5–10, 10–20, 20–30 and 30–50 cm) in the field using a metal ruler and spatula. These sub-samples were acidified with 1N hydrochloric acid and rinsed to remove the inorganic carbon before the organic carbon content was quantified using an Elementar Vario EL Cube CHNS analyzer.